JP6803850B2 - Surface-treated steel sheet for battery containers - Google Patents

Description

The present invention relates to a surface-treated steel sheet for a battery container.

In recent years, portable devices have been used in various fields such as audio devices and mobile phones, and alkaline batteries as primary batteries, nickel-metal hydride batteries as secondary batteries, lithium ion batteries and the like have been widely used as their operating power sources. Such batteries are required to have a longer life and higher performance as the performance of the equipment to be mounted is improved, and a battery container filled with a power generation element composed of a positive electrode active material or a negative electrode active material is also a battery. It is required to improve the performance as an important component of.

As a surface-treated steel sheet for forming such a battery container, for example, in Patent Documents 1 and 2, an iron-nickel diffusion layer is formed by forming a nickel plating layer on the steel sheet and then performing a heat treatment. Surface-treated steel sheets are disclosed.
On the other hand, with the demand for higher capacity and lighter weight of batteries, a battery container having a thin can wall for improving the floor area ratio is required for the battery container. For example, as in Patent Documents 3 and 4, it is known that processing is performed so that the thickness of the can wall of the battery container after processing becomes thinner than the thickness of the surface-treated steel sheet before processing.

Japanese Unexamined Patent Publication No. 2014-009401 Japanese Unexamined Patent Publication No. 6-2104 International Publication No. 2009/107318 International Publication No. 2014/156002

However, in Patent Documents 1 and 2, since the heat treatment conditions for forming the iron-nickel diffusion layer are high temperature or long time, the obtained surface-treated steel sheet is iron and nickel-plated on the base steel sheet. Mutual diffusion of the layer with nickel is likely to proceed. When the present inventors perform heat treatment under conventional heat treatment conditions, the amount of iron eluted from the inner surface of the battery container may increase when the battery is used as a battery after being processed into a battery container, resulting in higher corrosion resistance. We obtained the finding that it may easily decrease. Iron exposed during the formation of the battery container was considered preferable because it improves the battery characteristics, but according to the research by the present inventors, when the nickel plating layer formed before the heat treatment is thin, the exposure of iron may increase locally. It was revealed. When the amount of elution increases, the corrosion resistance may be more likely to decrease.

Further, in Patent Documents 3 and 4, there is a problem that by reducing the thickness of the can wall of the battery container, the amount of iron eluted on the inner surface of the battery container may increase, and the corrosion resistance of the inner surface of the battery container decreases. was there.

An object of the present invention is to provide a surface-treated steel sheet for a battery container having excellent corrosion resistance even when the thickness of the can wall is reduced to improve the floor area ratio when the battery container is used.

According to the present invention, a steel plate, an iron-nickel diffusion layer formed on the inner surface of the battery container of the steel plate, and a nickel layer formed on the iron-nickel diffusion layer and forming the outermost layer. When the Fe strength and Ni strength are continuously measured from the surface of the surface-treated steel plate for a battery container in the depth direction by a high-frequency glow discharge emission spectroscopic analyzer. The thickness of the iron-nickel diffusion layer, which is the difference (D2-D1) between the depth (D1) at which the Fe strength indicates the first predetermined value and the depth (D2) at which the Ni intensity indicates the second predetermined value, is a 0.04～0.31Myuemu, wherein the iron - the total amount of nickel contained in the nickel diffusion layer and the nickel layer, 4.4 g / ^{m 2} or more, the battery container surface is less than 10.8 g / ^{m 2} A treated steel plate is provided. The depth (D1) indicating the first predetermined value is a depth indicating an intensity of 10% with respect to the saturation value of the Fe intensity measured by the measurement, and is a depth indicating the second predetermined value. (D2) is a depth that shows an intensity of 10% with respect to the maximum value when the measurement is further performed in the depth direction after the Ni intensity shows a maximum value by the above measurement.

In the surface-treated steel sheet for a battery container of the present invention, the average crystal grain size of the surface portion of the nickel layer is preferably 0.2 to 0.6 μm.
In the surface-treated steel sheet for a battery container of the present invention, the thickness of the nickel layer is preferably 0.4 to 1.2 μm.
In the surface-treated steel sheet for a battery container of the present invention, the Vickers hardness (HV) measured at a load of 10 gf in the nickel layer is preferably 200 to 280.

According to the present invention, a battery container made of the above-mentioned surface-treated steel plate for a battery container is provided.
Further, according to the present invention, a battery including the above-mentioned battery container is provided.

Furthermore, according to the present invention, on the surface to be the battery container inner surface of the steel sheet, a nickel amount 4.4 g / ^{m 2} or more, and nickel plating step of forming a nickel plating layer of less than 10.8 g / ^{m 2,}
The steel sheet on which the nickel plating layer is formed is heat-treated by holding it at a temperature of 450 to 600 ° C. for 30 seconds to 2 minutes to diffuse iron-nickel having a thickness of 0.04 to 0.31 μm. Provided is a method for producing a surface-treated steel sheet for a battery container, which comprises a heat treatment step of forming a layer and a nickel layer constituting the outermost layer .

According to the present invention, it is possible to provide a surface-treated steel sheet for a battery container having excellent corrosion resistance even when the thickness of the can wall is reduced to improve the floor area ratio when the battery container is used. Further, according to the present invention, it is possible to provide a battery container and a battery obtained by using such a surface-treated steel plate for a battery container.

It is a perspective view which shows one Embodiment of the battery which applied the surface-treated steel plate for a battery container which concerns on this invention. It is sectional drawing which follows the line II-II of FIG. It is an embodiment of the surface-treated steel sheet for a battery container according to the present invention, and is an enlarged cross-sectional view of part III of FIG. It is a figure for demonstrating the method of manufacturing the surface-treated steel plate for a battery container shown in FIG. It is a graph which shows the result of having measured the Fe intensity and Ni intensity by the high frequency glow discharge emission spectrophotometer about the surface-treated steel sheet for a battery container of an Example and a comparative example. It is a graph which shows the result of having measured the surface hardness of the surface-treated steel sheet for a battery container of an Example and a comparative example. It is a photograph which shows the reflected electron image of the surface-treated steel plate for a battery container of an Example and a comparative example. It is a photograph which shows the reflected electron image, the elemental map of iron, and the elemental map of nickel about the inner surface of a battery container formed from the surface-treated steel plate for a battery container of Example 1. It is a photograph which shows the reflected electron image, the elemental map of iron and the elemental map of nickel about the inner surface of a battery container formed from the surface-treated steel plate for a battery container of Example 2. It is a photograph which shows the reflected electron image, the elemental map of iron, and the elemental map of nickel about the inner surface of a battery container formed from the surface-treated steel plate for a battery container of Comparative Example 1. It is a photograph which shows the reflected electron image, the elemental map of iron, and the elemental map of nickel about the inner surface of the battery container formed from the surface-treated steel plate for the battery container of Comparative Example 2. It is a photograph which shows the reflected electron image of the surface-treated steel plate for a battery container of a reference example. It is an enlarged photograph of the reflected electron image shown in FIG. It is a graph which shows the result of having measured the exposed area ratio of iron about the inner surface of a battery container formed from the surface-treated steel plate for a battery container of an Example and a comparative example. It is a graph which shows the result of having measured the surface hardness of the steel sheet which formed the nickel plating layer after heat treatment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The surface-treated steel sheet for a battery container according to the present invention is processed into an outer shape corresponding to a desired battery shape. The battery is not particularly limited, and examples thereof include an alkaline battery as a primary battery, a nickel hydrogen battery as a secondary battery, a lithium ion battery, and the like, and the present invention relates to a member of the battery container of these batteries. A surface-treated steel plate for a battery container can be used. In the following, the present invention will be described in an embodiment in which the surface-treated steel plate for a battery container according to the present invention is used for the positive electrode can constituting the battery container of an alkaline battery.

FIG. 1 is a perspective view showing an embodiment of an alkaline battery 2 to which a surface-treated steel plate for a battery container according to the present invention is applied, and FIG. 2 is a cross-sectional view taken along the line II-II of FIG. In the alkaline battery 2 of this example, the positive electrode mixture 23 and the negative electrode mixture 24 are filled inside the bottomed cylindrical positive electrode can 21 via the separator 25, and the negative electrode is formed on the inner surface side of the opening of the positive electrode can 21. A sealing body composed of a terminal 22, a current collector 26, and a gasket 27 is crimped. A convex positive electrode terminal 211 is formed in the center of the bottom of the positive electrode can 21. An exterior 29 is attached to the positive electrode can 21 via an insulating ring 28 in order to impart insulating properties and improve design.

The positive electrode can 21 of the alkaline battery 2 shown in FIG. 1 is a surface-treated steel sheet for a battery container according to the present invention, which is subjected to a deep drawing method, a drawing ironing method (DI processing method), a drawing stretch processing method (DTR processing method), and the like. Alternatively, it can be obtained by molding by a processing method that combines stretching processing and ironing processing after drawing processing. Hereinafter, the configuration of the surface-treated steel sheet for a battery container (surface-treated steel sheet 1) according to the present invention will be described with reference to FIG.

FIG. 3 is an enlarged cross-sectional view showing a portion III of the positive electrode can 21 shown in FIG. 2, in which the upper side is the inner surface of the alkaline battery 2 of FIG. 1 (the surface in contact with the positive electrode mixture 23 of the alkaline battery 2). ) Corresponds to. As shown in FIG. 3, the surface-treated steel plate 1 of the present embodiment is formed by forming an iron-nickel diffusion layer 12 and a nickel layer 14 on a steel plate 11 constituting the base material of the surface-treated steel plate 1.

In the surface-treated steel sheet 1 of the present embodiment, the thickness of the iron-nickel diffusion layer 12 measured by the high-frequency glow discharge emission spectroscopic analyzer is 0.04 to 0.31 μm, and the iron-nickel diffusion layer 12 and the total amount of nickel contained in the nickel layer 14, 4.4 g / ^{m 2} or more and less than 10.8 g / ^{m 2.} As a result, the surface-treated steel sheet 1 of the present embodiment has excellent corrosion resistance even when the thickness of the can wall is reduced to improve the floor area ratio when the battery container is used.
Further, in the present embodiment, the nickel layer 14 preferably has an average crystal grain size of 0.2 to 0.6 μm on the surface portion. As a result, the surface-treated steel sheet 1 of the present embodiment becomes more excellent in corrosion resistance when used as a battery container.

<Steel plate 11>
The steel sheet 11 of the present embodiment is not particularly limited as long as it is excellent in moldability, but is, for example, low carbon aluminum killed steel (carbon content 0.01 to 0.15% by weight) and carbon content of 0. Ultra-low carbon steel of .003% by weight or less, or non-aging ultra-low carbon steel obtained by adding Ti, Nb, etc. to the ultra-low carbon steel can be used. The thickness of the steel sheet is not particularly limited, but is preferably 0.2 to 0.5 mm. If it is too thick, the amount of heat required for diffusion may be insufficient and the diffusion layer may not be sufficiently formed. If it is too thin, the thickness required for a later battery can cannot be secured, or heat is transferred quickly, making it difficult to control the thickness of the diffusion layer.

In the present embodiment, the hot-rolled plates of these steels are pickled to remove surface scale (oxide film), then cold-rolled, then electrolytically washed, then annealed, temper-rolled, or After the cold rolling and electrolytic cleaning, the steel sheet 11 is subjected to temper rolling without annealing.

<Iron-nickel diffusion layer 12, nickel layer 14>
In the surface-treated steel plate 1 of the present embodiment, the iron-nickel diffusion layer 12 is formed by forming a nickel plating layer 13 on the steel plate 11 and then performing a thermal diffusion treatment to form an iron forming the steel plate 11 and a nickel plating layer. It is a layer in which iron and nickel are mutually diffused, which is formed by thermally diffusing the nickel constituting 13. The nickel layer 14 is a layer in which the portion of the nickel plating layer 13 near the surface layer on which iron has not diffused is recrystallized and softened by heat when the heat diffusion treatment is performed.

By forming the iron-nickel diffusion layer 12 obtained by such heat diffusion treatment, when the surface-treated steel sheet 1 is used as a battery container, the steel sheet comes into direct contact with the electrolytic solution or the like constituting the battery over a wide area. Further, by having the iron-nickel diffusion layer 12 that relaxes the potential difference between the nickel of the nickel layer 14 and the iron of the steel sheet 11, the corrosion resistance and the battery characteristics can be improved. it can. Further, by forming the iron-nickel diffusion layer 12, the adhesion between the steel plate 11 and the nickel layer 14 can be improved.

The nickel plating layer 13 for forming the iron-nickel diffusion layer 12 can be formed on the steel plate 11 by using, for example, a nickel plating bath. As the nickel plating bath, a plating bath usually used for nickel plating, that is, a watt bath, a sulfamic acid bath, a boron fluoride bath, a chloride bath and the like can be used. For example, the nickel plating layer 13 uses a watt bath having a bath composition of nickel sulfate 200 to 350 g / L, nickel chloride 20 to 60 g / L, and boric acid 10 to 50 g / L, and has a pH of 3.0 to 4.8 (pH 3.0 to 4.8). It can be formed at a pH of 3.6 to 4.6), a bath temperature of 50 to 70 ° C., and a current density of 10 to 40 A / dm ² (preferably 20 to 30 A / dm ² ).

As the nickel plating layer, glossy plating containing sulfur is not preferable because it may deteriorate the battery characteristics. However, in the present invention, not only matte plating containing no sulfur in an amount of unavoidable impurities or more, but also semi-glossy plating is used. Applicable. The hardness of the layer obtained by plating is harder than that of matte plating in semi-gloss plating, but the hardness of semi-gloss plating is about the same as or slightly higher than that of matte plating by the heat treatment for forming the diffusion layer in the present invention. This is to become. When semi-gloss plating is formed as the nickel plating layer, a semi-bright agent may be added to the plating bath. The semi-brightening agent is not particularly limited as long as it is a semi-brightening agent that does not contain sulfur in the nickel plating layer after plating (for example, the content is 0.05% or less in the measurement with fluorescent X-ray), but is not particularly saturated. Aliphatic unsaturated alcohols such as polyoxy-ethylene adducts of alcohols, unsaturated carboxylic acids, formaldehyde, coumarin and the like can be used.

In the present embodiment, as shown in FIG. 4, the above-mentioned nickel plating layer 13 is formed on the steel plate 11, and then the iron-nickel diffusion layer 12 and the nickel layer 14 are formed by performing a thermal diffusion treatment. A surface-treated steel sheet 1 as shown in 3 can be obtained.

In the present embodiment, the amount of nickel in the nickel plating layer 13 before the heat diffusion treatment corresponds to the total amount of nickel contained in the iron-nickel diffusion layer 12 and the nickel layer 14 obtained by the heat diffusion treatment.

The total amount of nickel contained in the iron-nickel diffusion layer 12 and the nickel layer 14 obtained by the heat diffusion treatment (the amount of nickel in the nickel plating layer 13 before the heat diffusion treatment) is 4.4 g / m ² or more and 10 .8g / ^m may be less than ^2, but preferably 5.5 g / ^{m 2} or more and less than 10.8 g / ^{m 2,} more preferably 6.5 g / ^{m 2} or more, is less than 10.8 g / ^{m 2} .. If the total amount of nickel contained in the iron-nickel diffusion layer 12 and the nickel layer 14 is too small, the effect of improving the corrosion resistance by nickel is insufficient, and when the obtained surface-treated steel sheet 1 is used as a battery container, the corrosion resistance is lowered. Resulting in. On the other hand, if the total amount of nickel contained in the iron-nickel diffusion layer 12 and the nickel layer 14 is too large, the thickness of the can wall becomes thick when the obtained surface-treated steel plate 1 is used as a battery container, and the battery container. The internal volume becomes smaller (the floor area ratio decreases). The total amount of nickel contained in the iron-nickel diffusion layer 12 and the nickel layer 14 is, for example, the total amount of nickel contained in the iron-nickel diffusion layer 12 and the nickel layer 14 which can be measured by ICP analysis method (total amount). It can be obtained by a method of calculating based on (weight). Alternatively, the total amount of nickel contained in the iron-nickel diffusion layer 12 and the nickel layer 14 is nickel-plated by performing fluorescent X-ray measurement after the nickel plating layer 13 is formed and before the thermal diffusion treatment is performed. It can also be obtained by a method of measuring the adhesion amount of nickel atoms constituting the layer 13 and calculating based on the measured adhesion amount.

The conditions for the heat diffusion treatment may be appropriately selected according to the thickness of the nickel plating layer 13, but the heat treatment temperature is 450 to 600 ° C., more preferably 480 to 590 ° C., still more preferably 500 to 550 ° C. The soaking time in the heat treatment is preferably 30 seconds to 2 minutes, more preferably 30 to 100 seconds, and even more preferably 45 to 90 seconds. Further, in the heat treatment, the time including the temperature raising / cooling time in addition to the soaking time is preferably 2 to 7 minutes, more preferably 3 to 5 minutes. As the method of heat diffusion treatment, the continuous annealing method is preferable from the viewpoint that the heat treatment temperature and the heat treatment time can be easily adjusted within the above ranges.

In the present invention, the iron-nickel diffusion layer 12 can be formed between the steel plate 11 and the nickel layer 14 by performing the heat diffusion treatment as described above, and as a result, the surface-treated steel plate 1 Can be configured to have an iron-nickel diffusion layer 12 and a nickel layer 14 on the steel plate 11 in this order from the bottom (Ni / Fe-Ni / Fe).

In the present embodiment, the iron-nickel diffusion layer 12 thus formed may have a thickness of 0.04 to 0.31 μm measured by a high-frequency glow discharge emission spectroscopic analyzer, preferably 0.05. It is ~ 0.27 μm, more preferably 0.08 to 0.25 μm, still more preferably 0.09 to 0.20 μm. If the thickness of the iron-nickel diffusion layer 12 is too thin, the adhesion of the nickel layer 14 may decrease in the obtained surface-treated steel sheet 1. On the other hand, if the thickness of the iron-nickel diffusion layer 12 is too thick, the exposed amount of iron in the nickel layer 14 of the obtained surface-treated steel sheet 1 becomes large, and as a result, the inner surface of the battery container is used as a battery. The amount of iron eluted from the iron increases, and the corrosion resistance decreases.

The thickness of the iron-nickel diffusion layer 12 is such that the Fe strength and Ni strength of the surface-treated steel sheet 1 are continuously changed in the depth direction from the outermost surface to the steel sheet 11 by using a high-frequency glow discharge emission spectroscopic analyzer. It can be obtained by measuring.

Specifically, first, the Fe intensity in the surface-treated steel sheet 1 is measured by using a high-frequency glow discharge emission spectroscopic analyzer until the Fe intensity is saturated, and the Fe intensity is determined based on the saturation value of the Fe intensity. The depth of 10% of the saturation value is defined as the boundary between the nickel layer 14 and the iron-nickel diffusion layer 12. For example, it will be described with reference to FIG. 5A, which is a measurement result of the surface-treated steel sheet 1 of the embodiment described later. In FIG. 5A, the vertical axis shows the Fe intensity and the Ni intensity, and the horizontal axis shows the measurement time when measured in the depth direction from the surface of the surface-treated steel sheet 1 by the high-frequency glow discharge emission spectroscopic analyzer. Is shown.

In the present embodiment, first, the saturation value of Fe intensity is obtained based on the measurement result of Fe intensity. The saturation value of Fe intensity is obtained from the time change rate of Fe intensity (Fe intensity change / sec). The rate of change in Fe intensity with time increases sharply when Fe is detected after the start of measurement, decreases after the maximum value, and stabilizes near zero. The saturation value is when it stabilizes near zero, and the time change rate of Fe intensity is specifically 0.02 (Fe intensity / sec) or less. The measurement time in the depth direction is the Fe intensity. Can be regarded as saturated.
In the example shown in FIG. 5 (A), the saturation value of Fe intensity is about 70 with a measurement time of about 20 seconds, and the depth at which Fe intensity is about 7 which is 10% of the saturation value is nickel. It can be detected as a boundary between the layer 14 and the iron-nickel diffusion layer 12.

On the other hand, the boundary between the iron-nickel diffusion layer 12 and the steel plate 11 can be detected as follows. That is, when the Ni strength of the surface-treated steel plate 1 was measured using a high-frequency glow discharge emission spectroscopic analyzer, a maximum value was extracted from the obtained graph of the change in Ni strength, and the Ni strength showed the maximum value. After that, the depth of 10% of the maximum value is determined to be the boundary between the iron-nickel diffusion layer 12 and the steel plate 11. For example, referring to FIG. 5 (A), since the maximum value of Ni strength is a value of about 70 in the measurement time of about 9 seconds, the depth of Ni strength is about 7 which is 10% of the maximum value. Can be detected as the boundary between the nickel plating layer 13 and the steel plate 11.

Then, in the present embodiment, the thickness of the iron-nickel diffusion layer 12 can be obtained based on the boundary of each layer determined as described above. Specifically, when measured using a high-frequency glow discharge emission spectroscopic analyzer, the Ni intensity shows its maximum value starting from the time when the Fe intensity becomes 10% of the saturation value. After that, the measurement time until the strength becomes 10% with respect to the maximum value can be calculated, and the thickness of the iron-nickel diffusion layer 12 can be obtained based on the calculated measurement time.
In order to determine the thickness of the iron-nickel diffusion layer 12 of the surface-treated steel plate 1 based on the measurement time, a high-frequency glow discharge issuance spectroscopic analysis of a nickel-plated steel plate having a known plating thickness and not subjected to thermal diffusion treatment is performed. The depth thickness calculated as the iron-nickel diffusion layer, which can be seen in the measured figure (for example, FIG. 5 (C) showing the measurement result of Comparative Example 1 described later), is the surface-treated steel plate 1 which is the actual measurement target. It is necessary to deduct when calculating the iron-nickel diffusion layer 12 of. That is, the thickness of the iron-nickel diffusion layer 12 portion calculated from the graph of FIG. 5 (A) (starting from the time when the Fe intensity becomes 10% of the saturation value in FIG. 5 (A)). , The value obtained by converting the measurement time from the time when the Ni strength reaches the maximum value to 10% of the maximum value into the thickness), and similarly from the graph of FIG. 5 (B). By subtracting the calculated thickness, the actual thickness of the iron-nickel diffusion layer 12 in the graph of FIG. 5 (A) can be obtained.
In the present invention, the thickness calculated as the iron-nickel diffusion layer by performing high-frequency glow discharge issuance spectroscopic analysis on the non-heat-treated nickel-plated steel sheet having the known plating thickness as described above is defined as the "reference thickness". The difference between D1 and D2 (D2-D1) refers to the one obtained by subtracting the reference thickness as described above.
In addition, in the measurement with the high-frequency glow discharge emission spectroscopic analyzer, as the thickness of the nickel plating layer increases, the reference thickness calculated from the measurement of the nickel plating layer becomes thicker. Therefore, when obtaining the iron-nickel diffusion layer, Check the standard thickness for each plating adhesion amount, or measure the standard thickness with a sample before performing two or more types of heat treatment with different plating adhesion amounts, and the relational expression between the plating adhesion amount and the standard thickness. It is desirable to obtain and calculate.

In addition, by measuring the nickel-plated steel plate that has not been heat-diffused, the relationship between the depth time (measurement time by the high-frequency glow discharge emission spectroscopic analyzer) and the actual thickness can be obtained. It can be converted into the thickness of the iron-nickel diffusion layer 12 and the thickness of the nickel layer 14 of the surface-treated steel plate 1 to be actually measured by using (a numerical value indicating the relationship between the depth time and the actual thickness). ..

When the thickness of the iron-nickel diffusion layer 12 is measured by the high-frequency glow discharge emission spectrophotometer in this way, the iron-nickel diffusion is caused by the performance and measurement conditions of the high-frequency glow discharge emission spectroscopy analyzer. There may be a detection limit for the thickness of the layer 12. For example, a nickel-plated heat-treated steel plate 1 prepared by using a steel plate having a surface roughness Ra of 0.05 to 3 μm measured by a stylus type roughness meter as the steel plate 11 is measured by a high-frequency glow discharge emission spectroscopic analyzer. When measured at φ5 mm, the thickness detectable region (detection limit value on the shape) by the high-frequency glow discharge emission spectroscopic analyzer is about 0.04 μm, and the iron-nickel diffusion layer measured by the high-frequency glow discharge emission spectroscopic analyzer. When the thickness of 12 is equal to or less than the detection limit value, the thickness of the iron-nickel diffusion layer 12 can be considered to be more than 0 μm and less than 0.04 μm. That is, when the nickel-plated layer 13 is formed on the steel plate 11 and then the iron-nickel diffusion layer 12 and the nickel layer 14 are formed by performing a thermal diffusion treatment, the iron-is produced by a high-frequency glow discharge emission spectroscopic analyzer. When the thickness of the nickel diffusion layer 12 is measured, even if it is equal to or less than the detection limit value, the thickness of the iron-nickel diffusion layer 12 can be considered to be more than 0 μm and less than 0.04 μm. When the nickel-plated steel plate 13 is formed on the steel plate 11 and then the nickel-plated steel plate is obtained without heat diffusion treatment, the iron-nickel diffusion layer 12 is not formed on the nickel-plated steel plate. It can be regarded as (the thickness of the iron-nickel diffusion layer 12 is 0).

The thickness of the iron-nickel diffusion layer 12 becomes larger as the heat treatment temperature is higher or the heat treatment time is longer because mutual diffusion between iron and nickel is more likely to proceed. Since iron and nickel diffuse with each other, the formed iron-nickel diffusion layer 12 spreads to the steel plate 11 side with respect to the interface between the steel plate 11 and the nickel plating layer 13 before diffusion, but to the nickel plating layer 13 side. Also spreads. If the heat treatment temperature is too high or the heat treatment time is too long, the iron-nickel diffusion layer 12 becomes thick and the nickel layer 14 becomes thin. For example, the thickness of the iron-nickel diffusion layer 12 is more than 0.3 μm. The present inventors have found that when such a surface-treated steel sheet is formed into a battery container, there is an increase in the amount of elution which is considered to be caused by an increase in iron exposure. The exposure of iron on the inner surface of the battery container is not only when the thickness of the nickel layer 14 on the surface-treated steel sheet 1 is almost eliminated and the iron reaches the surface layer, but also when the iron does not reach the surface layer in the state of the surface-treated steel sheet 1. However, it is considered that the cause is that a large amount of iron is exposed on the inner surface of the battery container and a locally exposed portion appears. In this case, when the surface-treated steel sheet 1 is stored or used as a battery container for a long period of time, iron elutes from the locally exposed portion of iron into the electrolytic solution, which is generated as the iron elutes. There is a risk that the internal pressure inside the battery will rise due to the gas generated.
In particular, the present inventors have performed processing such that the nickel plating layer is thinned or the thickness of the can wall after forming the battery can is made thinner than the thickness of the surface-treated steel sheet before forming in order to increase the capacity of the battery. When this is done, it has been found that the corrosion resistance may be more likely to decrease, and it has been found that the surface-treated steel sheet 1 of the present embodiment exhibits remarkably corrosion resistance even under such severe processing conditions. Further, in order to increase the capacity of the battery, it is conceivable to reduce the thickness of the nickel plating layer and the thickness of the can wall, but all of these means are factors that reduce the corrosion resistance of the battery container. Become. The present inventors have found a new problem of achieving both these means for increasing the capacity and improvement of corrosion resistance in the conventional surface-treated steel sheet, and have found a new configuration capable of increasing the capacity. is there.

In the present embodiment, as described above, the surface-treated steel sheet 1, the iron - the total amount of nickel contained in the nickel diffusion layer and the nickel layer 4.4 g / m ² or more, compared of less than 10.8 g / m ² By controlling the temperature within a small range, the thickness of the can wall can be reduced when the battery container is used, and as a result, the floor area ratio of the obtained battery can be significantly improved. Moreover, according to the surface-treated steel sheet 1 of the present embodiment, by setting the thickness of the iron-nickel diffusion layer 12 to 0.04 to 0.31 μm or less, the thickness of the can wall when the battery container is used as described above. Even when the volume ratio is improved by thinning the battery container, the battery container can be made excellent in corrosion resistance. Conventionally, when the thickness of the can wall of the battery container is reduced, the amount of iron eluted on the inner surface of the battery container may increase, which may reduce the corrosion resistance of the inner surface of the battery container. .. On the other hand, as a method of improving the corrosion resistance when the battery container is used, there is a method of increasing the thickness of the iron-nickel diffusion layer and the nickel layer formed on the inner surface of the battery container. In this case, when the battery container is used. In addition, there is a problem that the thickness of the can wall becomes thick and the volume ratio decreases. Therefore, in the technique of the surface-treated steel sheet for a battery container, it is difficult to achieve both the floor area ratio and the corrosion resistance when the battery container is used. On the other hand, according to the present embodiment, the thickness of the iron-nickel diffusion layer 12 and the total amount of nickel contained in the iron-nickel diffusion layer 12 and the nickel layer 14 described above are controlled within the above ranges, respectively. This makes it possible to provide the surface-treated steel sheet 1 in which the volume ratio of the battery container and the corrosion resistance are highly balanced.

Further, conventionally, in a surface-treated steel sheet provided with a nickel plating layer and an iron-nickel diffusion layer, from the viewpoint of improving workability when molding as a battery container, from the viewpoint of improving the corrosion resistance of the battery container, adhesion of the iron-nickel diffusion layer From the viewpoint of ensuring the properties, a method of increasing the thickness of the iron-nickel diffusion layer to 0.5 μm or more has been known (for example, paragraph 0018 of JP-A-2009-263727). Here, in order to increase the thickness of the iron-nickel diffusion layer to 0.5 μm or more, it is necessary to set the conditions for the heat diffusion treatment after forming the nickel plating layer on the steel sheet for a long time or at a high temperature. .. For example, when the condition of the heat diffusion treatment is long, it is known that the heat treatment temperature is 400 to 600 ° C. and the heat treatment time is 1 to 8 hours. Further, when the condition of the heat diffusion treatment is high temperature, it is known that the heat treatment temperature is 700 to 800 ° C. and the heat treatment time is 30 seconds to 2 minutes. In such a situation, when the heat diffusion treatment is performed under the above-mentioned long-term or high-temperature conditions, the present inventors heat-diffuse the iron of the steel sheet constituting the surface-treated steel sheet, and the obtained surface treatment We obtained the finding that the amount of iron eluted increases when a steel sheet is molded into a battery container, and as a result, as described above, gas is generated inside the battery, and the inside of the battery is caused by the generation of gas. It was found that the internal pressure of the battery may rise. In addition, when the heat treatment temperature is 700 to 800 ° C. for 30 seconds to 2 minutes, the hardness of the nickel layer 14 is excessively lowered, so that there is a problem that seizure to the mold is increased.

On the other hand, according to the present embodiment, for the surface-treated steel sheet 1, the thickness of the iron-nickel diffusion layer 12 is 0.04 to 0.31 μm, and the thickness of the nickel contained in the iron-nickel diffusion layer and the nickel layer is the total amount of 4.4 g / m ² or more, by controlling the range of less than 10.8 g / m ^2, the surface treated steel sheet 1 on the inner surface at the shaping of the battery container, the area of iron of the steel sheet is exposed It is possible to reduce the amount and improve the corrosion resistance when the surface-treated steel sheet 1 is used as the battery container, and in addition, it is possible to further improve the workability when the surface-treated steel sheet 1 is processed into the battery container. It was.

Further, in the present embodiment, the thickness of the nickel layer 14 after the heat diffusion treatment is preferably 0.5 to 1.20 μm, more preferably 0.60 to 1.20 μm, and further preferably 0.70 to 1.17 μm. Is. When the thickness of the nickel layer 14 after the thermal diffusion treatment is controlled to a relatively thin range as described above, the effect of improving the corrosion resistance of the iron-nickel diffusion layer 12 is sufficiently ensured, and the battery container is used. The wall thickness can be reduced and the volume inside the battery container can be increased. As a result, the amount of contents such as the positive electrode mixture 23 and the negative electrode mixture 24 to be filled in the battery container can be increased, and the battery characteristics of the obtained battery can be improved. The thickness of the nickel layer 14 after the thermal diffusion treatment can be determined by detecting the boundary between the nickel layer 14 and the iron-nickel diffusion layer 12 by measurement using the high-frequency glow discharge emission spectroscopic analyzer described above. That is, the measurement time is calculated from the time when the measurement of the surface of the surface-treated steel sheet 1 is started by the high-frequency glow discharge emission spectroscopic analyzer to the time when the Fe intensity becomes 10% of the saturation value. , The thickness of the nickel layer 14 can be obtained based on the calculated measurement time.

Further, in the present embodiment, the nickel layer 14 after the heat diffusion treatment has an average crystal grain size of a surface portion of preferably 0.2 to 0.6 μm, more preferably 0.3 to 0.6 μm, still more preferably. It is 0.3 to 0.5 μm. In the present embodiment, the average crystal grain size of the surface portion of the nickel layer 14 is not particularly limited, but if the average crystal grain size is too small, the plating stress remains inherent, and in this case, When molding as a battery container, the surface-treated steel plate 1 may be deeply cracked to reach the steel plate 11, and the iron of the steel plate 11 may be exposed. In this case, iron may elute from the exposed portion of the steel sheet 11, and the internal pressure inside the battery may increase due to the gas generated by the elution of iron. On the other hand, as described above, if the surface-treated steel plate 1 is cracked to reach the steel plate 11, a problem occurs. However, from the viewpoint of improving the battery characteristics of the battery container, the battery container of the surface-treated steel plate 1 is used. It is preferable that fine cracks are generated on the inner surface side of the above. Regarding this point, if the average crystal grain size of the surface portion of the nickel layer 14 is too large, the hardness of the nickel layer 14 may become too low (the nickel layer 14 becomes too soft), and in this case, When the surface-treated steel sheet 1 is molded as a battery container, fine cracks cannot be generated on the inner surface of the battery container, so that the effect of improving the battery characteristics, that is, the contact between the battery container and the positive electrode mixture due to the cracks The effect of increasing the area, lowering the internal resistance of the battery, and improving the battery characteristics may not be sufficiently obtained.

According to the present embodiment, the thickness of the iron-nickel diffusion layer 12 of the surface-treated steel sheet 1 is relatively thin, 0.04 to 0.31 μm, even when the thickness of the nickel plating layer 13 is relatively thin. By doing so, the area where the iron of the steel sheet is exposed on the inner surface side when the surface-treated steel sheet 1 is molded into the battery container is suppressed, and the corrosion resistance when the surface-treated steel sheet 1 is used as the battery container is improved. Is now possible. In addition, according to the present embodiment, by controlling the average crystal grain size of the surface portion of the nickel layer 14 to 0.2 to 0.6 μm, the workability when processing the surface-treated steel sheet 1 into a battery container can be improved. It has become possible to improve it further. Further, according to the present embodiment, since the thickness of the iron-nickel diffusion layer 12 and the nickel layer 14 is relatively thin, it is advantageous in terms of cost when manufacturing the surface-treated steel sheet 1, and the battery. When the battery is assembled by molding into a container, the internal capacity of the battery container can be increased, which leads to improvement of battery characteristics.

The average crystal grain size of the surface portion of the nickel layer 14 tends to increase as the heat treatment temperature in the thermal diffusivity treatment increases. However, the present inventors have determined that the size of the average crystal grain size depends on the temperature range. I found that it would grow in size. The crystal grains become larger in the one subjected to the heat treatment even at a low temperature, for example, 300 ° C., as opposed to the one not subjected to the heat treatment. When the heat treatment temperature is between 400 and 600 ° C., the crystal grain size becomes slightly larger as the temperature rises, but the difference in crystal grain size depending on the temperature is not so large. When the heat treatment temperature exceeds 700 ° C., the average crystal grain size sharply increases. Therefore, the average crystal grain size of the surface portion of the nickel layer 14 can be adjusted by controlling the heat treatment temperature of the thermal diffusion treatment. In particular, by suppressing the coarsening of the average crystal grain size and making the surface hardness of the nickel layer 14 harder, the effect of improving the battery characteristics and suppressing the seizure of the nickel layer 14 on the mold during processing into a battery container is achieved. The heat treatment temperature is particularly preferably 430 to 550 ° C. That is, by setting the heat treatment temperature within the above range and making the surface hardness of the nickel layer 14 harder, when molding as a battery container, the surface-treated steel plate 1 is fine enough not to reach the inner surface side of the battery container. Cracks can be generated, and the cracks can increase the contact area between the battery container and the positive electrode mixture, reduce the internal resistance of the battery, and further improve the battery characteristics.

In the present embodiment, the average crystal grain size of the surface portion of the nickel layer 14 can be determined, for example, by measuring the surface of the surface-treated steel sheet 1 with a scanning electron microscope (SEM) and using the obtained backscattered electron image. it can.

Specifically, first, the surface of the surface-treated steel sheet 1 is etched as necessary, and then the surface of the surface-treated steel sheet 1 is measured with a scanning electron microscope (SEM), for example, as shown in FIG. 7A. .. Note that FIG. 7A is an image showing a reflected electron image obtained by measuring the surface-treated steel sheet 1 of the embodiment described later at a magnification of 10,000 times. Then, an arbitrary number (for example, four) of straight lines having a length of 10 μm is drawn on the obtained backscattered electron image. Then, for each straight line, the crystal grain size d is obtained by the formula d = 10 / (n + 1) based on the number n of crystal grains located on the straight line, and the average of the crystal grain sizes d obtained for each straight line is obtained. The value can be the average crystal grain size of the surface portion of the nickel plating layer 13.

Further, in the present embodiment, the surface hardness of the nickel layer 14 after the heat diffusion treatment is the Vickers hardness (HV) measured with a load of 10 gf, preferably 200 to 280, and more preferably 210 to 250. By setting the surface hardness of the nickel layer 14 after the heat diffusion treatment within the above range, the workability when processing the obtained surface-treated steel sheet 1 into a battery container is improved, and the surface-treated steel sheet 1 is used for the battery container. Corrosion resistance is improved.

In the present embodiment, as a method for controlling the thickness of the iron-nickel diffusion layer 12 and the total amount of nickel contained in the iron-nickel diffusion layer and the nickel layer in the surface-treated steel sheet 1 within the above ranges, respectively, A method of performing the heat diffusion treatment under the above-mentioned conditions can be mentioned. That is, a method of forming the nickel plating layer 13 on the steel sheet 11 and then performing the heat diffusion treatment under the conditions of a heat treatment temperature of 450 to 600 ° C. and a heat treatment time of 30 seconds to 2 minutes can be mentioned.
Further, in the present embodiment, as a method of controlling the average crystal grain size of the surface portion of the nickel layer 14 in the above-mentioned range with respect to the obtained surface-treated steel sheet 1, a method of performing a thermal diffusion treatment under the same conditions can be mentioned. Be done. That is, a method of forming the nickel plating layer 13 on the steel sheet 11 and then performing the heat diffusion treatment under the conditions of a heat treatment temperature of 450 to 600 ° C. and a heat treatment time of 30 seconds to 2 minutes can be mentioned.

The thickness of the iron-nickel diffusion layer 12 tends to increase as the heat treatment temperature in the heat diffusion treatment increases and the heat treatment time increases. Therefore, the thickness of the iron-nickel diffusion layer 12 and the ratio of (thickness of the iron-nickel diffusion layer 12 / thickness of the nickel layer 14) can be adjusted by controlling the heat treatment temperature and the heat treatment time of the heat diffusion treatment. it can. However, since the iron-nickel diffusion layer is difficult to form at 300 ° C., the viewpoint of controlling the thickness of the iron-nickel diffusion layer 12 and the ratio (thickness of the iron-nickel diffusion layer 12 / thickness of the nickel layer 14) within the above range. Therefore, it is preferable to carry out the heat diffusion treatment at 480 ° C. or higher.

The surface-treated steel sheet 1 of the present embodiment is configured as described above.

The surface-treated steel sheet 1 of the present embodiment includes a deep drawing method, a drawing ironing method (DI processing method), a drawing stretch processing method (DTR processing method), or a processing method in which stretching processing and ironing processing are used in combination after drawing processing. Therefore, the positive electrode can 21 of the alkaline battery 2 shown in FIGS. 1 and 2 and the battery container of other batteries are molded and used.

<Manufacturing method of surface-treated steel sheet 1>
Next, a method for manufacturing the surface-treated steel sheet 1 of the present embodiment will be described.

First, the steel plate 11 is prepared, and as described above, the steel plate 11 is nickel-plated to form the nickel-plated layer 13 on the inner surface of the battery container of the steel plate 11. The nickel plating layer 13 is preferably formed not only on the inner surface of the battery container of the steel plate 11 but also on the opposite surface. When the nickel plating layer 13 is formed on both sides of the steel sheet 11, the inner surface of the battery container and the outer surface of the battery container of the steel sheet 11 are formed by using plating baths having different compositions. The nickel plating layers 13 having different surface roughness and the like may be formed, but from the viewpoint of improving the manufacturing efficiency, the nickel plating layers 13 are formed on both sides of the steel sheet 11 in one step using the same plating bath. Is preferable.

Next, the steel sheet 11 on which the nickel plating layer 13 is formed is heat-diffused under the above-mentioned conditions to thermally diffuse the iron constituting the steel sheet 11 and the nickel constituting the nickel plating layer 13 to iron. -The nickel diffusion layer 12 and the nickel layer 14 are formed. As a result, the surface-treated steel sheet 1 as shown in FIG. 3 is obtained.

In this embodiment, the obtained surface-treated steel sheet 1 may be subjected to temper rolling. Thereby, the surface roughness of the surface of the surface-treated steel sheet 1 which is the inner surface of the battery container can be adjusted, and when the surface-treated steel sheet 1 is used as the battery container, the contact area between the battery container and the positive electrode mixture can be adjusted. It can be increased, the internal resistance of the battery can be lowered, and the battery characteristics can be improved.

As described above, the surface-treated steel sheet 1 of the present embodiment is manufactured.

In the surface treated steel sheet 1 of the present embodiment, as described above, the iron - the total amount of nickel contained in the nickel diffusion layer and the nickel layer 4.4 g / m ² or more, a relatively small of less than 10.8 g / m ² The alkaline battery 2 obtained by controlling the range and setting the thickness of the iron-nickel diffusion layer 12 measured by the high-frequency glow discharge emission spectroscopic analyzer to a relatively thin range of 0.04 to 0.31 μm or less. The thickness of the can wall of the battery container is reduced to significantly improve the volume ratio, and the area where iron of the steel plate is exposed on the inner surface side of the battery container is suppressed to improve the corrosion resistance of the battery container. Can be made to. Further, as described above, the hardness of the nickel layer 14 can be made appropriate by setting the average crystal grain size of the surface portion of the nickel layer 14 to preferably 0.2 to 0.6 μm. When molding as a battery container, the surface-treated steel sheet 1 is more effectively prevented from being exposed to iron due to deep cracks, and fine cracks are generated on the inner surface of the battery container to improve the battery characteristics. An excellent effect of improving more effectively can be obtained. Further, as described above, by setting the thickness of the nickel layer 14 to preferably 0.5 μm or more, the corrosion resistance when the surface-treated steel sheet 1 is used in the battery container is further improved, and the gas inside the battery is further improved. It is possible to more effectively prevent the occurrence and the increase in the internal pressure inside the battery due to this. Therefore, the surface-treated steel plate 1 of the present embodiment can be suitably used as, for example, a battery using an alkaline electrolytic solution such as an alkaline battery or a nickel-metal hydride battery, or a battery container such as a lithium ion battery.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

<< Reference example A >>
As the original plate, a steel plate 11 obtained by annealing a cold-rolled low-carbon aluminum killed steel plate (thickness 0.25 mm) having the following chemical composition was prepared.
C: 0.045% by weight, Mn: 0.23% by weight, Si: 0.02% by weight, P: 0.012% by weight, S: 0.009% by weight, Al: 0.063% by weight, N: 0.0036% by weight, balance: Fe and unavoidable impurities

Then, the prepared steel sheet 11 is subjected to alkaline electrolytic degreasing and pickling by immersion in sulfuric acid, and then electrolytic plating is performed under the following conditions so that the amount of nickel adhered to the steel sheet 11 is 10.7 g / m ^2. The plating layer 13 was formed. After that, the thickness of the nickel plating layer 13 was determined by fluorescent X-ray measurement to determine the amount of adhesion thereof. The results are shown in Table 1.
Bath composition: nickel sulfate 250 g / L, nickel chloride 45 g / L, boric acid 45 g / L
pH: 3.5-4.5
Bath temperature: 60 ° C
Current density: 20A / dm ²
Energizing time: 18 seconds

Next, the steel sheet 11 on which the nickel plating layer 13 was formed was subjected to thermal diffusion treatment under the conditions of a heat treatment temperature of 430 ° C., a heat treatment time of 1 minute, and a reducing atmosphere by continuous annealing to obtain an iron-nickel diffusion layer 12 and nickel. The layer 14 was formed to obtain a surface-treated steel plate 1.

Next, the obtained surface-treated steel sheet 1 was subjected to temper rolling under the condition of an elongation rate of 1%.

Then, using the surface-treated steel plate 1 after temper rolling, the thickness of the iron-nickel diffusion layer 12 and the nickel layer 14 is measured, the surface hardness of the nickel layer 14 is measured, and the average crystal of the nickel layer 14 is measured according to the following method. The particle size was measured and the surface was observed with a scanning electron microscope (SEM).

<Measurement of thickness of iron-nickel diffusion layer 12 and nickel layer 14>
With respect to the surface-treated steel plate 1, changes in Fe strength and Ni strength are continuously measured in the depth direction from the outermost surface to the steel plate 11 using a high-frequency glow discharge emission spectrophotometer, and the Fe strength is measured with respect to the saturation value. Starting from the time when the strength reaches 10%, after the Ni strength shows its maximum value, the measurement time until the time when the strength reaches 10% with respect to the maximum value is calculated, and the calculated measurement time is used. Based on this, the thickness of the iron-nickel diffusion layer 12 was determined. When determining the thickness of the iron-nickel diffusion layer 12, first, the result of high-frequency glow discharge issuance spectroscopic analysis of a nickel-plated steel sheet (Comparative Example 1) that has not been subjected to the thermal diffusion treatment described later (FIG. 5 (FIG. 5). Regarding C)), the Ni strength is the thickness of the iron-nickel diffusion layer (in FIG. 5C, starting from the time when the Fe strength becomes 10% of the saturation value). After showing the maximum value, the measurement time until the strength became 10% of the maximum value was converted into the thickness) was measured as the reference thickness. The reference thickness was 0.30 μm. Then, by subtracting this reference thickness from the measurement result of the thickness of the iron-nickel diffusion layer 12 of the surface-treated steel sheet 1 of Example 1, the actual thickness of the iron-nickel diffusion layer 12 in Example 1 can be obtained. I asked. The nickel layer 14 starts at the time when the surface of the surface-treated steel sheet 1 is measured by the high-frequency glow discharge emission spectroscopic analyzer and ends at the time when the Fe intensity becomes 10% of the saturation value. The thickness of the nickel layer 14 was determined based on the calculated measurement time. Then, based on the measurement result, the ratio of the thickness of the iron-nickel diffusion layer 12 to the thickness of the nickel layer 14 (thickness of the iron-nickel diffusion layer 12 / thickness of the nickel layer 14) was determined. The results are shown in FIG. 5 (A) and Table 1. In Table 1, the ratio of (thickness of iron-nickel diffusion layer 12 / thickness of nickel layer 14) is described as "thickness ratio Fe-Ni / Ni".
In addition, in the measurement with the high-frequency glow discharge emission spectroscopic analyzer, as the thickness of the nickel plating layer increases, the reference thickness calculated from the measurement of the nickel plating layer becomes thicker. Therefore, when obtaining the iron-nickel diffusion layer, Confirm the standard thickness for each plating amount, or measure the standard thickness with a sample before performing two or more types of heat treatment with different plating amounts, and obtain the relational expression between the plating amount and the standard thickness. It is desirable to calculate.

<Measurement of surface hardness of nickel layer 14>
The Vickers hardness (HV) of the nickel layer 14 of the surface-treated steel sheet 1 was measured by a microhardness meter (manufactured by Akashi Seisakusho Co., Ltd., model number: MVK-G2) using a diamond indenter under the conditions of load: 10 gf and holding time: 10 seconds. ) Was measured to measure the surface hardness. The results are shown in FIG.

<Measurement of average crystal grain size of nickel layer 14>
First, the surface of the surface-treated steel sheet 1 was etched. Specifically, 0.1 ml of an aqueous solution prepared by dissolving copper sulfate hydrate at a concentration of 200 g / L is added dropwise to the surface of the surface-treated steel sheet 1, and immediately after that, 0.1 ml of hydrochloric acid is added dropwise and held for 30 seconds. Etched, then washed with water and dried. Next, a reflected electron image on the surface of the surface-treated steel plate 1 was obtained by a scanning electron microscope (SEM), and four straight lines were drawn on the obtained reflected electron image as shown in FIG. 7 (A). According to the method described above, the average crystal grain size of the nickel layer 14 was calculated from the number of crystal grains located on each straight line. The results are shown in FIG. 7 (A) and Table 1.

<Observation of the surface with a scanning electron microscope (SEM)>
Using the surface-treated steel plate 1, a battery container of LR6 (JIS standard) was produced so that the nickel layer 14 was on the inner surface side of the battery container and the thickness of the can wall was 0.15 mm. Then, with respect to the obtained battery container, the portions 10 mm, 25 mm, and 40 mm from the bottom were measured by a scanning electron microscope (SEM) and energy dispersive X-ray analysis to obtain a reflected electron image and an elemental map of iron. And obtained an elemental map of nickel. The results are shown in FIGS. 8 (A) to 8 (C). In FIGS. 8 (A) to 8 (C), the image described as "Image" is a reflected electron image, and the image described as "Feka" is an elemental map of iron, which is referred to as "Nika". The image described is an elemental map of nickel. In the elemental map of iron, the part where the kα ray due to iron is observed is shown in white. Similarly, in the elemental map of nickel, the part where the kα ray due to nickel is observed appears in white. The image of the elemental map of iron was binarized with image processing software, and the area ratio of the white portion to the entire obtained image (that is, the exposed area ratio of iron) was measured. The results are shown in FIG. 14 and Table 2.

<< Example 1 >>
A surface-treated steel sheet 1 was produced in the same manner as in Reference Example A except that the heat treatment temperature for performing the thermal diffusion treatment on the steel sheet 11 on which the nickel plating layer 13 was formed was set to 600 ° C., and measurement and observation were carried out in the same manner. went. The results are shown in FIGS. 5 (B), 6, 7 (B), 9, 14 and Tables 1 and 2.

<< Comparative Example 1 >>
A nickel-plated steel sheet was produced under the same conditions as in Example 1 except that the steel sheet 11 on which the nickel-plated layer 13 was formed was not subjected to any heat diffusion treatment or temper rolling. Then, as described above, the produced nickel-plated steel sheet is measured by high-frequency glow discharge issuance spectroscopic analysis, the measurement result shown in FIG. 5C is obtained, and the thickness measured as the iron-nickel diffusion layer ( In FIG. 5C, starting from the time when the Fe intensity becomes 10% of the saturation value, the Ni intensity shows the maximum value, and then the intensity is 10% of the maximum value. The value obtained by converting the measurement time up to that point into thickness) was measured as the reference thickness. Further, in Comparative Example 1, the surface hardness and the average crystal grain size of the nickel plating layer 13 were measured instead of the nickel layer 14. In Comparative Example 1, the surface was not etched when the average crystal grain size of the nickel plating layer 13 was measured. The results are shown in FIGS. 5 (C), 6, 7 (C), 10, 14 and Tables 1 and 2.

<< Comparative Example 2 >>
A surface-treated steel sheet 1 was produced in the same manner as in Example 1 except that the heat treatment temperature at which the heat diffusion treatment was performed on the steel sheet 11 on which the nickel plating layer 13 was formed was 700 ° C. and temper rolling was not performed. , And the same measurement and observation were performed. In Comparative Example 2, the surface was not etched when measuring the average crystal grain size of the nickel layer 14. The results are shown in FIGS. 5 (D), 6, 7 (D), 11, 14 and Tables 1 and 2.

<< Reference example 1 >>
As the original plate, the same steel plate 11 as in Example 1 was prepared. Then, the prepared steel sheet 11 is subjected to alkaline electrolytic degreasing and pickling by immersion in sulfuric acid, and then electrolytically plated under the following conditions to form a nickel plating layer 13 on the steel sheet 11 so as to have a thickness of 20 μm. did. The thickness of the nickel plating layer 13 was determined by fluorescent X-ray measurement.
Bath composition: nickel sulfate 250 g / L, nickel chloride 45 g / L, boric acid 45 g / L
pH: 3.5-4.5
Bath temperature: 60 ° C

Then, the steel plate 11 on which the nickel plating layer 13 was formed was measured with a scanning electron microscope (SEM) to obtain a reflected electron image on the surface. The results are shown in FIGS. 12 (A) and 13 (A). Note that FIG. 13 (A) is an enlarged image of FIG. 12 (A).

Next, with respect to the steel plate 11 on which the nickel plating layer 13 was formed, the surface hardness of the nickel plating layer 13 was measured by the same method as the measurement of the surface hardness of the nickel layer 14 described above. The results are shown in FIG.

<< Reference example 2 >>
In the same manner as in Reference Example 1, the steel plate 11 was prepared and the nickel plating layer 13 was formed on the steel plate 11. Next, the steel sheet 11 on which the nickel plating layer 13 was formed was subjected to thermal diffusion treatment under the conditions of a heat treatment temperature of 300 ° C., a heat treatment time of 41 seconds, and a reducing atmosphere by continuous annealing to obtain an iron-nickel diffusion layer 12 and nickel. The layer 14 was formed to obtain a surface-treated steel plate 1.

Then, the surface hardness of the nickel layer 14 was measured by obtaining a reflected electron image on the surface of the obtained surface-treated steel sheet 1 in the same manner as in Reference Example 1. The results are shown in FIG.

<< Reference Examples 3 to 8 >>
The heat treatment temperature for performing the thermal diffusion treatment on the steel sheet 11 on which the nickel plating layer 13 is formed is 400 ° C. (Reference Example 3), 500 ° C. (Reference Example 4), 600 ° C. (Reference Example 5), 700 ° C. (Reference Example 5). A surface-treated steel sheet 1 was produced in the same manner as in Reference Example 2 except that the temperatures were set to Reference Example 6), 800 ° C. (Reference Example 7), and 900 ° C. (Reference Example 8), and measurements were performed in the same manner as in Reference Example 1. .. The results are shown in FIGS. 12 (B) to 12 (E), 13 (B) to 13 (E), and 15.

As shown in Table 1, the thickness of the iron-nickel diffusion layer 12 is 0.04 to 0.31 μm, and the total amount of nickel contained in the iron-nickel diffusion layer and the nickel layer is 4.4 g / m ^2. As mentioned above, in Reference Example A and Example 1 which are less than 10.8 g / m ² , the steel plate 11 is diffused to the surface of the surface-treated steel plate 1 as shown by the element map of iron in FIGS. 8 and 9. No kα rays of iron were observed. Specifically, as shown in FIGS. 14 and 2, in Reference Example A and Example 1, the area ratio of the white portion (the exposed area ratio of iron) to the entire element map of iron is as small as 11% or less, and the steel plate No kα rays of iron derived from the diffusion of 11 to the surface of the surface-treated steel sheet 1 were observed. In the elemental map of iron in FIGS. 8 and 9, white parts where kα rays of iron were observed are sparsely present, but this is very slight due to fine flaws on the surface of the surface-treated steel sheet 1. It is considered that the cause is that the steel plate 11 is exposed, and it can be determined that the cause is not that the steel plate 11 is diffused to the surface of the surface-treated steel plate 1 by the heat diffusion treatment.

Further, as shown in FIG. 7, in Reference Example A and Example 1 in which the thermal diffusion treatment was performed, as compared with Comparative Example 1 in which the thermal diffusion treatment was not performed, the higher the heat treatment temperature of the thermal diffusion treatment, the more crystals were crystallized. It can be seen that the particles of are larger (that is, the crystal grain size is larger). It is considered that this is because the higher the heat treatment temperature, the more the recrystallization of the particles constituting the nickel layer 14 progresses and the larger the crystal grain size.

Further, as shown in FIG. 15, from the measurement results of the surface hardness in Reference Examples 1 to 8, the surface hardness of the nickel layer 14 is lowered by making the heat treatment temperature of the thermal diffusion treatment higher than 300 ° C. (nickel). It can be confirmed that the plating layer 13 is softened). From this, it is considered that the recrystallization of the particles constituting the nickel layer 14 is progressing. In Reference Examples 1 to 8, since the thickness of the nickel plating layer 13 is as thick as 20 μm, the nickel layer 14 can be appropriately used without being affected by the underlying steel plate 11 when measuring the surface hardness. The hardness could be measured. Therefore, in Reference Example A and Example 1 in which the heat treatment temperature of the thermal diffusion treatment is 400 ° C. or 630 ° C., recrystallization of the particles constituting the nickel layer 14 proceeds, and the surface hardness of the nickel layer 14 becomes appropriate. It is thought that it is.

On the other hand, as shown in Table 1, in Comparative Example 1 in which the thermal diffusion treatment was not performed, the average crystal grain size of the nickel layer 14 was less than 0.2 μm. As a result, in Comparative Example 1, the surface hardness of the nickel layer 14 becomes too high, and when molding as a battery container, the surface-treated steel sheet 1 is deeply cracked to reach the steel sheet 11, and the iron of the steel sheet 11 is formed. It is considered that the battery container is exposed and the corrosion resistance of the battery container is lowered.
Further, as shown in Table 1, and in Comparative Example 2 in which the heat treatment temperature of the heat diffusion treatment was 700 ° C., the thickness of the iron-nickel diffusion layer 12 was 0.5 μm or more, and the nickel layer 14 had a thickness of 0.5 μm or more. The thickness became less than 0.85 μm, and as a result, as shown in the elemental map of iron in FIG. 11, kα rays of iron derived from the diffusion of iron in the steel plate 11 to the vicinity of the surface of the surface-treated steel plate 1 were observed. It was. That is, compared with FIGS. 8 and 9 described above, in the elemental map of iron in FIG. 11, there are many white spots derived from the kα line of iron, and they are further solidified (actually, FIGS. 14 and 2). In the iron element map of FIGS. 8 and 9 (Reference Example A, Example 1), the area ratio of the white portion (the ratio of the exposed area of iron) to the entire image is 11% or less, while FIG. In the elemental map of iron in Comparative Example 2), it is as high as 15% or more at 25 mm and 40 mm from the bottom of the battery container).

In particular, in Comparative Example 2 in which the heat treatment temperature is 700 ° C., any of 10 mm, 25 mm and 40 mm from the bottom of the battery container is compared with Reference Example A and Example 1 in which the heat treatment temperatures are 430 ° C. and 600 ° C. Also, the proportion of exposed area of iron is increasing. Such an increase in the exposed area ratio of iron in Comparative Example 2 is particularly remarkable at 25 mm and 40 mm from the bottom of the battery container. This is because when the surface-treated steel sheet 1 is used to form the battery container, the farther from the bottom of the battery container, that is, the closer to the mouth portion of the battery container, the more the surface-treated steel sheet 1 is drawn in the stretching direction (when forming into the battery container). A force that is squeezed in the press direction) and the circumferential direction is applied, resulting in higher load machining.

In Comparative Example 2 in which the heat treatment temperature was 700 ° C., the heat diffusion treatment proceeded excessively and the thickness of the nickel layer 14 became too thin, so that the portion subjected to the above-mentioned high load processing (bottom of the battery container). It is considered that the iron exposure of the steel plate 11 has increased especially in the portion far from the steel plate 11. This can also be confirmed from the elemental map of iron and the elemental map of nickel shown in FIG. That is, referring to FIG. 11, in the elemental map of iron, the proportion of the exposed area of iron increases as the distance from the bottom of the battery container increases, and the portion where iron is collectively exposed increases. Comparing such an elemental map of iron with the corresponding elemental map of nickel, the position of the part where iron is collectively exposed in the elemental map of iron has a small amount of nickel detected in the elemental map of nickel. It corresponds to the position of the part that is. As a result, in Comparative Example 2, it can be confirmed that the exposure of iron is increased in the portion where the thickness of the nickel layer 14 is thin.

From this, since the iron of the steel sheet 11 diffused to the vicinity of the surface of the surface-treated steel sheet 1, the diffusion of iron-nickel proceeded too much and the nickel layer on the surface layer became too thin, so that the surface-treated steel sheet 1 was press-molded. At that time, it is considered that the nickel coating on the inner surface of the battery can becomes incomplete. Further, as shown in Table 1, in Comparative Example 2, the average crystal grain size of the nickel layer 14 was more than 0.6 μm, and the Vickers hardness was lower than that of Reference Example A and Example 1 from FIG.

In Comparative Example 1 in which the heat diffusion treatment was not performed, Reference Example A in which the heat diffusion treatment was performed at 430 ° C. and 600 ° C. was carried out with respect only to the numerical values of the exposed area ratio of iron shown in FIGS. 14 and 2. The value tends to be lower than that of Example 1. However, in Comparative Example 1, when referring to the element map shown in FIG. 10, as compared with the element maps of Reference Example A and Example 1 shown in FIGS. 8 and 9, iron exposure occurs collectively at a specific position. This tendency is particularly remarkable in the elemental map at a position 10 mm from the bottom of the battery container. It is considered that this is because the nickel plating layer 13 on the surface is too hard in Comparative Example 1 in which the thermal diffusion treatment was not performed. That is, when the surface-treated steel sheet 1 is formed into a battery container, the bottom surface portion of the battery container comes into contact with the circumferential portion of the punch used for pressing and is bent, but the surface of Comparative Example 1 Since the nickel plating layer 13 on the surface of the treated steel sheet 1 is too hard, deep cracks are likely to occur on the surface during this bending process. Therefore, when the surface-treated steel sheet 1 of Comparative Example 1 is used as a battery container, if deep cracks occur on the surface, iron is locally exposed and iron is eluted into the electrolytic solution. Gas may be generated inside the battery due to the elution of iron. When such a gas is generated, the internal pressure inside the battery may rise.

<< Example 2 >>
As the original plate, a steel plate 11 obtained by annealing a cold-rolled low-carbon aluminum killed steel plate (thickness 0.25 mm) having the following chemical composition was prepared.
C: 0.045% by weight, Mn: 0.23% by weight, Si: 0.02% by weight, P: 0.012% by weight, S: 0.009% by weight, Al: 0.063% by weight, N: 0.0036% by weight, balance: Fe and unavoidable impurities

Then, the prepared steel sheet 11 is subjected to alkaline electrolytic degreasing and pickling by immersion in sulfuric acid, and then electrolytic plating is performed under the following conditions so that the amount of nickel adhered to the steel sheet 11 is 8.9 g / m ^2. The plating layer 13 was formed. After that, the thickness of the nickel plating layer 13 was determined by fluorescent X-ray measurement to determine the amount of adhesion thereof.
Bath composition: nickel sulfate 250 g / L, nickel chloride 45 g / L, boric acid 45 g / L
pH: 3.5-4.5
Bath temperature: 60 ° C
Current density: 20A / dm ²
Energizing time: 16 seconds

Next, the steel sheet 11 on which the nickel plating layer 13 was formed was subjected to thermal diffusion treatment under the conditions of a heat treatment temperature of 480 ° C., a heat treatment time of 30 seconds, and a reducing atmosphere by continuous annealing to obtain an iron-nickel diffusion layer 12 and nickel. The layer 14 was formed to obtain a surface-treated steel plate 1.

Next, the obtained surface-treated steel sheet 1 was subjected to temper rolling under the condition of an elongation rate of 1%. The thickness of the surface-treated steel sheet 1 after temper rolling was 0.250 mm.

Then, using the surface-treated steel sheet 1, the thicknesses of the iron-nickel diffusion layer 12 and the nickel layer 14 were measured according to the method described above. Further, based on the measurement results, the ratio of the thickness of the iron-nickel diffusion layer 12 to the thickness of the nickel layer 14 (thickness of the iron-nickel diffusion layer 12 / thickness of the nickel layer 14) was determined. The results are shown in Table 3.

<< Examples 3 to 9 >>
The surface-treated steel sheet 1 is the same as in Example 3 except that the thickness of the nickel plating layer 13 and the conditions for continuous annealing (heat treatment conditions) for the steel sheet 11 on which the nickel plating layer 13 is formed are changed as shown in Table 3. Was obtained, and the measurement was performed in the same manner. The results are shown in Table 3.

<< Comparative Example 3 >>
A nickel-plated steel sheet was produced under the same conditions as in Example 3 except that neither continuous annealing nor temper rolling was performed after the nickel-plated layer 13 was formed. The results are shown in Table 3.

<< Comparative Examples 4 to 6 >>
The surface-treated steel sheet 1 is the same as in Example 3 except that the thickness of the nickel plating layer 13 and the conditions for continuous annealing (heat treatment conditions) for the steel sheet 11 on which the nickel plating layer 13 is formed are changed as shown in Table 3. Was obtained, and the measurement was performed in the same manner. The results are shown in Table 3.

Next, the corrosion resistance of the surface-treated steel sheets 1 of Examples 3 and 4 and Comparative Examples 4 to 6 and the nickel-plated steel sheets of Comparative Example 3 were evaluated when they were formed into a battery container according to the following method. went.

<Corrosion resistance evaluation (1)>
A blank was produced by punching the surface-treated steel sheet 1 into a predetermined shape with a press machine, and a battery container was produced by drawing under the following conditions so that the nickel layer 14 was on the inner surface side (nickel). When a plated steel plate was used, the battery container was prepared so that the nickel plating layer 13 was on the inner surface side.) That is, a tubular body was obtained by squeezing and ironing a blank using a squeezing and squeezing machine in which squeezing dies (or ironing dies) were arranged in 6 stages and a punch. A battery container was obtained by cutting the ear portion near the opening of the tubular body. For drawing, a die having a clearance set so that the thickness of the can wall at a position 10 mm from the bottom of the can after processing was ± 5% was used.
Next, the obtained battery container was filled with a solution of 10 mol / L potassium hydroxide, sealed, held at 60 ° C. for 480 hours, and then Fe ions eluted from the inner surface of the battery container into the solution. The elution amount was measured by radio frequency inductively coupled plasma emission spectroscopy (ICP) (ICPE-9000 manufactured by Shimadzu Corporation) and evaluated according to the following criteria. In the following criteria, if the evaluation was A or B, it was judged that the elution of iron from the inner surface of the battery container was sufficiently suppressed. The results are shown in Table 4.
A: Fe ion elution amount is less than 33 mg / L B: Fe ion elution amount is 33 to 35 mg / L
C: Fe ion elution amount exceeds 35 mg / L

As shown in Table 4, the thickness of the iron-nickel diffusion layer 12 is 0.04 to 0.31 μm, and the total amount of nickel contained in the iron-nickel diffusion layer and the nickel layer is 4.4 g / m ^2. As mentioned above, all of Examples 3 and 4 having a value of less than 10.8 g / m ² were found to have excellent corrosion resistance. That is, it was confirmed that Examples 3 and 4 have the same or higher corrosion resistance as those of Comparative Examples 5 and 6 based on Comparative Examples 5 and 6 having the same corrosion resistance as the conventional surface-treated steel sheet. Was done.

On the other hand, as shown in Table 4, in Comparative Example 3 in which the heat diffusion treatment was not performed, although the evaluation result of the corrosion resistance was good, the iron-nickel diffusion layer 12 was formed by not performing the heat diffusion treatment. It is considered that the adhesion of the nickel plating layer 13 is inferior due to this.
Further, even when the heat diffusion treatment is performed, if the thickness of the iron-nickel diffusion layer 12 becomes too thick due to the excessive heat diffusion treatment, iron is exposed on the surface of the nickel layer 14. As a result, when Comparative Example 6 having the same corrosion resistance as the conventional surface-treated steel sheet is used as a reference as in Comparative Example 5, the corrosion resistance is equal to or less than that of Comparative Example 6. It was.
Further, in the surface-treated steel sheet of Comparative Example 6, the total amount of nickel contained in the iron-nickel diffusion layer and the nickel layer is too large (the thickness of the nickel plating layer 13 is too thick), so that when used as a battery container, It is considered that the can wall becomes thick and the volume ratio decreases.

Next, the surface-treated steel sheets 1 of Examples 3 and 4 and Comparative Example 4 were subjected to the following methods.
A battery container was produced by performing squeezing and ironing with a higher load than the corrosion resistance evaluation (No. 1), and the corrosion resistance of the battery container was evaluated under stricter conditions.

<Corrosion resistance evaluation (2)>
As a 6-stage drawing die (or ironing die) in a drawing and ironing machine, corrosion resistance is obtained except that a battery container is manufactured by performing drawing and ironing processing with a higher load than the corrosion resistance evaluation (No. 1) as shown below. Similar to the evaluation (No. 1), the battery container was prepared and the amount of Fe ions eluted was measured, and the evaluation was performed according to the following criteria. The results are shown in Table 5.
For the squeezing process, a die having a clearance set so that the thickness of the can wall at a position 10 mm from the bottom of the can after processing was 0.15 mm was used.
The amount of Fe ions eluted from the inner surface of the battery container into the solution was evaluated according to the following criteria. In the following criteria, if the evaluation was A or B, it was judged that the elution of iron from the inner surface of the battery container was sufficiently suppressed.
A: Fe ion elution amount is less than 35 mg / L B: Fe ion elution amount is 35 to 38 mg / L
C: Fe ion elution amount exceeds 38 mg / L

As shown in Table 5, the thickness of the iron-nickel diffusion layer 12 is 0.04 to 0.31 μm, and the total amount of nickel contained in the iron-nickel diffusion layer and the nickel layer is 4.4 g / m ^2. As described above, Examples 3 and 4 having a value of less than 10.8 g / m ² are excellent in corrosion resistance even when a battery container is produced by performing squeezing and ironing with a higher load than the above-mentioned corrosion resistance evaluation (No. 1). Was the result.

On the other hand, as shown in Table 5, in Comparative Example 4 in which the thickness of the iron-nickel diffusion layer 12 became too thick due to the excessive thermal diffusion treatment, it is considered that iron was exposed on the surface of the nickel layer 14. The result was that the corrosion resistance was inferior when the battery container was manufactured by performing a high-load drawing and ironing process.

1 ... Surface-treated steel plate 11 ... Steel plate 12 ... Iron-nickel diffusion layer 13 ... Nickel plating layer 14 ... Nickel layer 2 ... Alkaline battery 21 ... Positive electrode can 211 ... Positive electrode terminal 22 ... Negative electrode terminal 23 ... Positive electrode mixture 24 ... Negative electrode mixture 25 ... Separator 26 ... Current collector 27 ... Gasket 28 ... Insulation ring 29 ... Exterior

Claims (7)

Steel plate and
An iron-nickel diffusion layer formed on the inner surface of the battery container of the steel plate,
A surface-treated steel sheet for a battery container, comprising a nickel layer formed on the iron-nickel diffusion layer and forming the outermost layer.
When the Fe strength and Ni strength are continuously measured from the surface of the surface-treated steel sheet for a battery container to the depth direction by a high-frequency glow discharge emission spectroscopic analyzer, the depth at which the Fe strength shows the first predetermined value ( The thickness of the iron-nickel diffusion layer, which is the difference (D2-D1) between D1) and the depth (D2) at which the Ni strength shows the second predetermined value, is 0.04 to 0.31 μm.
Wherein the iron - the total amount of nickel contained in the nickel diffusion layer and the nickel layer, 4.4 g / ^{m 2} or more, the battery case for surface treated steel sheet is less than 10.8 g / ^{m 2.}
(The depth (D1) indicating the first predetermined value is a depth indicating an intensity of 10% with respect to the saturation value of the Fe intensity measured by the measurement.
The depth (D2) indicating the second predetermined value is 10% of the maximum value when the measurement is further performed in the depth direction after the Ni intensity shows the maximum value by the measurement. Depth indicating strength. ) The surface-treated steel sheet for a battery container according to claim 1, wherein the average crystal grain size of the surface portion of the nickel layer is 0.2 to 0.6 μm. The surface-treated steel sheet for a battery container according to claim 1 or 2, wherein the nickel layer has a thickness of 0.4 to 1.2 μm. The surface-treated steel sheet for a battery container according to any one of claims 1 to 3, wherein the Vickers hardness (HV) measured at a load of 10 gf in the nickel layer is 200 to 280. A battery container made of a surface-treated steel plate for a battery container according to any one of claims 1 to 4 . A battery comprising the battery container according to claim 5 . On the surface to be battery container inner surface of the steel sheet, a nickel amount 4.4 g / ^{m 2} or more, and nickel plating step of forming a nickel plating layer of less than 10.8 g / ^{m 2,}
The steel sheet on which the nickel plating layer is formed is heat-treated by holding it at a temperature of 450 to 600 ° C. for 30 seconds to 2 minutes to diffuse iron-nickel having a thickness of 0.04 to 0.31 μm. A method for producing a surface-treated steel sheet for a battery container, comprising a heat treatment step of forming a layer and a nickel layer constituting the outermost layer .

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